Implementation React Native Offline Mode

        Hello coders we know In today's world of mobile applications, providing a seamless user experience is crucial. One essential feature is offline mode, which allows users to continue using an app even without an internet connection. Additionally, asynchronous API calls are necessary to fetch and update data in the background without blocking the user interface. This tutorial will explore how to implement offline mode and asynchronous API calls using AsyncStorage in a React Native application.

        To follow along with this tutorial, you should have a basic understanding of React Native and have a development environment set up on your machine. Ensure you have a recent version of Node.js installed and a working React Native project.

1. Install Dependencies

        Here I use react @react-native-async-storage/async-storage and fecth, @react-native-async-storage/async-storage to store data in local storage and fecth to make api calls; this fecth is a subordinate of javascript.

yarn add @react-native-async-storage/async-storage

2. Offline Mode Function

        Offline mode ensures that the app works properly even without an internet connection. To implement this, we will use AsyncStorage to store and retrieve data locally on our device.

        First, we create an AsyncStorage configuration file. In this file, there are 4 main functions that are used to run offline mode.

        The saveDataLocaly function functions to store data, from the input form that we created and is in JSON form, and what we need to know is that what we can store into local data using AsyncStorage is that the data must be in the form of a string, because the data we send is in the form of JSON we must change it to a string with 

        The retriveDataLocally function is used to call data according to the status sent in the props, and if you don't send the status, this function will return all data in AsyncStorage with the key 'myData', and of course the data that is returned is data that has been parsed.

        This third function is to store all data originating from the API and combine it with pre-existing local data. The question is why not use the previous function because the saveDataLocaly function is intended only for storing or adding data one by one from the input we made, and after that, online data with an offline status will be deleted and replaced with data with an online status originating from the API. The delete function is

        removeDataLocally function, the question is why should it be removed? This actually suits our needs, we can only update data that is local, but to make it easier for us to process data between online and offline data so that there are no clashes, all data that is local is deleted and replaced using data that is from APIs.

3. Offline Mode Implementation

        After we create a form according to our needs, we will always save the data into AsyncStorage with offline status and give it an offline ID from now on. The implementation is as below in the screen form.

        The saveDataLocally function is a function that we import from the function file that we created earlier. After our data has been saved locally,  we will implement a way to manage local data and data from the API when our device is online. This implementation is done in the screen list data file.

        above functions to call the function the first time after that screen is accessed.

        The syncDataWithApi function functions to send local data one by one when the device is online by calling the retriveDataLocally function with offline status and sending it to the back end with effect urlregisterToApi until local data with offline status is gone, and after successful registration to the local data API, it will be removed immediately using the removeDataLocally function. While registering data to the API, the above function will be asynchronously called to call data from the API using the getData() function.

        This getData function is to get data from the API using the urlGetDataFromApi, and after the data is obtained, the status in the data is updated to 'online', and then the data is saved locally using the saveDataOnlineToLocaly function. While this process is ongoing, the getData function will run another function, namely onSetData.

        The onSetData function will call local data with the retriveDataLocally function without sending the status parameter, which means it will call all local data, which will be put into state listData, and this data will be displayed using the default FlatList from react-native.

        The above code is a way to display data using FlatList.

        In this tutorial, we learned how to implement offline mode and asynchronous API calls using AsyncStorage in a React Native application. We explored the usage of AsyncStorage to store and retrieve data locally on the user's device. Additionally, we used the fecth to make asynchronous API calls and updated the stored data accordingly. By following the steps outlined above, you can enhance your React Native applications by providing a seamless user experience even in offline scenarios and ensuring smooth background data synchronization with APIs.

        Anything that can still be less clear, or there are errors in this tutorial, or any input that could be more efficient for offline mode implementation can leave a comment in this article, thank you. Happy Coding